[bug] User notification preferences page throws error after removing notification type and repopulating preferences

[pandafy]

Describe the bug
The populate_notification_preferences command does not delete the NotifiationSettings for undefined Notification Types, instead it flags them as deleted.

The REST API endpoint does not exclude the deleted NotificationSetting objects. Thus, opening the notification preferences page raises NotificationRenderException.

Steps To Reproduce
Steps to reproduce the behavior:

1. Ensure there's a superuser created in your project
2. Add a new notification type in openwisp_notifications/apps.py using the register_notification_type method
3. Run ./manage.py populate_notification_preferences command
4. Remove the code which adds the new notification type
5. Run ./manage.py populate_notification_preferences command which is supposed to delete NotificationSettings for undefined notification types.
6. Run django server and go to the user's notification preferences page

Expected behavior
User notification preferences are displayed.

Actual result
No notification preference is displayed. The application shows Error fetching notification settings. Please try again.

Other Notes

This bug was found while upgrading OpenWISP Controller from 1.1 to 1.2 (the api_task_error and api_task_recovery notification types were removed in openwisp-controller). Thus, the solution should also be tested manually with OpenWISP controller.

[pandafy]

Thinking out loud

We should re-consider the deletion logic for NotificationSetting objects. Earlier, it was possible to delete the objects from the admin. Now, the API does not allow it.

It will be more appropriate to make the REST API view conform to the deleted flag.

[Apeksha-22]

Hey Mentor!
I’m really interested in working on this bug. Could you assign it to me?

[Piyushkhobragade]

Hi @pandafy,

I’d like to investigate this issue.

From the description it seems the problem originates from populate_notification_preferences soft-deleting NotificationSetting objects for removed notification types while the REST API still includes those rows, which then triggers NotificationRenderException when the preferences page loads.

I’ll start by reproducing the scenario locally (add → populate → remove → populate) and trace how the API queryset handles the deleted flag, then determine whether the fix should live in the API layer or in the population/deletion logic.

I’ll report back with findings before opening a PR.